1. Field of the Invention
This invention relates to a suspension arm used in a suspension mechanism mounted on a vehicle.
2. Related Art
Conventionally, in a suspension mechanism mounted on a vehicle, a suspension arm connected with an another connecting bar in a vibration preventing condition and forms a link mechanism has been used. This suspension arm is manufactured by or made of mainly a ferrous material and formed by a press working or a forging. Recently, for lightening the suspension arm, a light metallic materials such as an aluminium alloy and the like formed by the forging have been adopted.
By the way, the suspension arm can have various shapes corresponding to an attached location thereof to the vehicle. For example, an upper arm attached to an upper portion of the suspension mechanism and a lower arm attached to a lower portion of the suspension arm have bent shapes such as an arch shape, V-shape or U-shape. However, when these bent suspension are formed by forging the aluminium alloy, the suspension arm of hollow shape is hardly formed, which makes further lightening of the suspension arm difficult.
In addition, when the suspension is comprised of an arm member and a pair of bearing members attached to both ends of the arm member, if whole of the suspension arm including the bearings are formed by the forging, a bearing to bearing distance between the bearing members provided at the both ends of the arm member requiring an especially high dimensional accuracy, can not be maintained in high accuracy. As a result, various cutting working become necessary after the forging for maintaining the dimensional accuracy, which introduces increase of a working man-hour and a manufacturing cost.